The word "lest" is meant to come after something else. It means "for fear that" or "or else" or something similar. So it's not clear what you're trying to say. I don't know what "very systems" built by "the most evil" you mean either. Is it supposed to be obvious what you're referring to?
I clicked the link and remain confused. The poem does have in common the term "lest we forget", but apparently nothing else. It's also used in a grammatically correct way in the poem, but not in your post, since it's not following anything.
That's the banality of evil.